chrome-icu: add dependencies related to xkbcommon USE.

This CL adds the dependencies to RDEPEND when USE flag "xkbcommon" is
enabled. This is identical to chromeos-chrome.ebuild, which will make
CQ more likely to catch potential errors of chrome-icu.ebuild by
testing chromeos-chrome.ebuild related to libxkbcommon.

BUG=none
TEST="emerge-nocturne chrome-icu" works.

Change-Id: Ibea728a7d4bf9b7324945306e909b8625300dcb0
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/chromiumos-overlay/+/2442914
Tested-by: Honglin Yu <honglinyu@chromium.org>
Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
Commit-Queue: Honglin Yu <honglinyu@chromium.org>
diff --git a/chromeos-base/chrome-icu/chrome-icu-9999.ebuild b/chromeos-base/chrome-icu/chrome-icu-9999.ebuild
index 1804360..e85f7cc 100644
--- a/chromeos-base/chrome-icu/chrome-icu-9999.ebuild
+++ b/chromeos-base/chrome-icu/chrome-icu-9999.ebuild
@@ -48,6 +48,7 @@
 	+thinlto
 	ubsan
 	verbose
+	xkbcommon
 	"
 
 # [Mod] clear REQUIRED_USE.
@@ -83,9 +84,16 @@
 # [Mod] chrome/icu depends on nothing. Blocking the canonical icu package can
 # let us notice the potential repetitions.
 # [Mod] Old Chrome ebuilds installed icudtl.dat.
+# Add `xkbcommon` related libraries to make xkbcommon handling identical with
+# chromeos-chrome. This will make it more likely to catch potential xkbcommon
+# related chromeos-icu.ebuild failures by testing chromeos-chrome.ebuild.
 RDEPEND="
 	!dev-libs/icu
 	!<chromeos-base/chromeos-chrome-83.0.4098.4
+	xkbcommon? (
+		x11-libs/libxkbcommon
+		x11-misc/xkeyboard-config
+	)
 "
 DEPEND="
 	net-print/cups
@@ -122,6 +130,10 @@
 		"enable_nacl=false"
 		"enable_nacl=false"
 		"icu_use_data_file=true"
+		# Add this to make xkbcommon handling identical with chromeos-chrome.
+		# This will make it more likely to catch potential xkbcommon related
+		# chromeos-icu.ebuild failures by testing chromeos-chrome.ebuild
+		"use_xkbcommon=$(usetf xkbcommon)"
 		# use_system_minigbm is set below.
 		# HarfBuzz and FreeType need to be built together in a specific way
 		# to get FreeType autohinting to work properly. Chromium bundles